JUST WATCHEDWhy the 2018 midterm elections matterReplayMore Videos …MUST WATCH (16 Videos)Why the 2018 midterm elections matterCNN poll: Most think Trump will lose in 2020Some Republicans not ready to back Trump in 2020Corker questions Trump 2020 bidRomney not committing to support Trump in 2020GOP senator won’t say if he backs Trump 2020 bid Mark Cuban may run in 2020 as a RepublicanSchwarzenegger: Kasich should run in 2020The Rock, Tom Hanks reveal 2020 campaignIs Oprah mulling a 2020 presidential run?Kasich, Hickenlooper mull 2020 unity ticketKasich: Rooting for Trump to ‘get it together’Pence: New York Times report is disgracefulPresident Trump has his first 2020 challengerGOP senator unsure if Trump will be 2020 nomineeSasse dodges question about 2020 W.H. runWashington (CNN)The generic congressional ballot has continued to tighten, according to a new CNN poll conducted by SSRS, with the Democrats’ edge over Republicans within the poll’s margin of sampling error for the first time this cycle. About six months out from Election Day, 47% of registered voters say they back the Democratic candidate in their district, 44% back the Republican. Voters also are divided almost evenly over whether the country would be better off with the Democrats in control of Congress (31%) or with the GOP in charge (30%). A sizable 34% — including nearly half of independent voters (48%) — say it doesn’t matter which party controls Congress. Related: Full poll resultsThe Democrats’ advantage in the generic ballot dipped from 16 points in February to six points in March to just three points now. The party’s advantage has waned among enthusiastic voters as Republican enthusiasm has grown (in March, 36% of Republican and Republican-leaning registered voters said they were very enthusiastic about voting; that’s up to 44% in the new poll), but the Democrats still have a double-digit lead among those most excited to vote this fall (53% of those who are very enthusiastic about voting say they’d back the Democrat in their district vs. 41% who say they favor the GOP candidate). Those enthusiastic voters also say by a 10-point margin that the nation would be better off with Democrats in control of Congress than Republicans. Related content from the CNN PollTrump approval steady amid rising optimism His approval is rising among these specific groupsMajority say US should not withdraw from Iran dealMelania Trump’s popularity jumpsDemocrats’ 2018 advantage is nearly goneBy 48% to 43%, registered voters say they would rather back a candidate who opposes Donald Trump than one who supports the President. That margin has narrowed from the 52% who opposed Trump to the 41% who supported him in January. Read MoreThe results come from the same poll this week that found nearly six in 10 saying that things in the country are going well amid improving approval ratings for the President’s handling of major issues, including the economy, immigration and foreign trade. Trump’s overall approval rating, however, held steady at 41%.CNN Poll: Trump approval steady amid rising outlook for the countryAbout two-thirds of voters (64%) say they consider Trump to be extremely or very important to their vote for Congress this year. Among enthusiastic voters, he’s an even larger factor: 78% consider Trump important to their vote this fall. And the poll suggests those voters who say the President matters deeply to their vote are more inclined to cast a ballot against him. Among the nearly four in 10 who say Trump will be extremely important to their vote this fall, 51% say they would rather support a candidate who opposes the President, while 46% prefer a candidate who supports Trump. On more traditional issue priorities, voters are now more apt to say the nation’s economy will be an important factor in their vote than they were in February (84% call it extremely or very important now, up from 79% in February), with immigration (from 72% important to 76% now) and taxes (from 67% important to 73% now) are also on the rise. At the same time, health care has dipped somewhat as a priority (from 83% important to 80%, with the most meaningful shift coming in the share who call it “extremely important,” which dipped from 53% in February to 46% now), along with sexual harassment (from 64% to 58%) and the Russia investigation (from 45% important in February to 40% now). Gun policy, an issue that spiked in salience for voters following the school shooting in Parkland, Florida, in mid-February, has remained a top issue, with 76% calling it extremely or very important to their vote this fall, about the same as the 78% who said so then. The gap between Democrats and Republicans on this issue has narrowed, though. In February, Democrats were significantly more likely than Republicans to consider the issue important (87% to 72%) and now there is no meaningful difference between the two parties in the share who consider the issue important (79% of Democrats and 76% of Republicans call it important).Partisan shifts are driving other changes in issue priorities as well. Republicans are increasingly likely to consider immigration important (80% now vs. 70% in February) while Democrats are turning away from the issue (78% important now vs. 83% in February). The shift on taxes is more due to an increase in salience among Republicans (+13 in importance to 83%) than Democrats (+6 to 72% important), and the softening on sexual harassment stems more from GOP dropoff (from 48% important then to 38% now) than any fade in Democratic attention to the issue (80% rated it important in both polls). Majorities of voters on both sides of the aisle say they want their parties to nominate candidates who share their positions on major issues more than wanting candidates who can beat their counterparts on the other side. Republicans and Republican-leaning voters are more apt to feel this way, 76% prefer candidates who share their views vs. 67% among Democrats and Democratic-leaning voters. Perhaps surprisingly, the most enthusiastic voters on each side are a bit less wedded to issue purity: 61% of Democrats who are very enthusiastic about voting say they want candidates who agree with their views, and on the GOP side, that figure stands at 70%.Pelosi on Democratic candidates who oppose her: 'Just win, baby'Views of both parties’ leaders in the House of Representatives break negative, according to the poll. About half, 49%, have an unfavorable view of Nancy Pelosi, with 30% saying they have a favorable take on the Democratic House leader, and 46% view current Speaker Paul Ryan negatively, 38% positively. Republicans are more positive toward Ryan (67% favorable) than Democrats are toward Pelosi (57% see her favorably). The Democratic Party as a whole is viewed more positively than the Republican Party: 44% have a favorable take on the Democrats, 39% on the Republicans. The CNN poll was conducted by SSRS May 2-5 among a random national sample of 1,015 adults reached on landlines or cellphones by a live interviewer. Results for the full sample have a margin of sampling error of plus or minus 3.6 percentage points, it is 3.8 points for the subset of 901 registered voters.