Republicans' growing unity behind their presidential nominee, Donald Trump, has helped pull him just 1 percentage point behind Hillary Clinton and has placed GOP leaders who resist him in a vulnerable position, according to the latest Washington Post-ABC News Tracking Poll.

A majority of all likely voters say they are unmoved by the FBI's announcement Friday that it may review additional emails from Clinton's time as secretary of state. Just more than 6 in 10 voters say the news will make no difference in their vote, while just more than 3 in 10 say it makes them less likely to support her; 2 percent say they are more likely to back her as a result.

The issue may do more to reinforce preferences of voters opposed to Clinton than swing undecided voters. Roughly two-thirds of those who say the issue makes them less likely to support Clinton are Republicans or Republican-leaning independents (68 percent), while 17 percent lean Democratic and 9 percent are independents who lean toward neither party.

When asked about House Speaker Paul D. Ryan's decision not to campaign for Trump in the final weeks before the election, two-thirds of Republican-leaning likely voters disapprove of the Wisconsin Republican's move (66 percent), including nearly half who disapprove “strongly” (48 percent). Barely 1 in 5 approve of Ryan's decision (21 percent).

The Post-ABC Tracking Poll continues to find a very tight race, with Clinton at 46 percent and Trump at 45 percent among likely voters in interviews from Tuesday through Friday. The two major-party nominees for president are followed by Libertarian Gary Johnson, at 4 percent, and the Green Party's Jill Stein, at 2 percent. The result is similar to a 47-to-45 Clinton-Trump margin in the previous wave released Saturday, though it is smaller than what was found in other surveys this week. When likely voters are asked to choose between Clinton and Trump alone, Clinton stands at 49 percent, and Trump is at 46 percent, a statistically insignificant margin.

Greater Republican unity has buoyed Trump's rising support, which has wavered throughout the year. Trump's 87 percent support among self-identified Republicans, ticking up from 83 percent last week, nearly matches Clinton's 88 percent support among Democrats. Independents also have moved sharply in Trump's direction, from favoring Clinton by eight points one week ago to backing Trump by 19 points.

Clinton maintains clear edge on qualifications, but not on empathy

Clinton is still widely seen as more qualified for the presidency, leading that measure by an 18-point margin, 54 to 36 percent. She has held a clear advantage over Trump in qualifications throughout the campaign.

But Trump receives more unified backing among those who see him as better qualified. Fully 99 percent of this group supports him, compared with Clinton's 84 percent support among those who see her as better qualified. Seven percent of this group supports Trump, while 4 percent are for Johnson and 2 percent are for Stein.

Clinton also lost a once-large advantage on empathy, a trait on which voters now split 46 percent for her and 43 percent for Trump when asked which candidate understands the problems of people like them. Clinton had led Trump by an eight-point margin on this measure in early September among likely voters and by a 20-point margin among all adults in August.

Clinton has a narrow eight-point edge over Trump on which candidate has stronger moral character, 46 to 38 percent. A sizable 13 percent said that neither candidate possesses this trait. A larger share of Trump supporters than Clinton supporters say that neither candidate has strong moral character (12 percent vs. 2 percent).

Republicans' reactions to Ryan

Ryan's decision not to campaign for Trump this fall has proved unpopular among his fellow partisans. This comes as Ryan's status as House speaker is in peril because of Republican infighting.

Rejection of Ryan's stance swells to 75 percent among Republicans and GOP-leaning independents who identify as “very conservative” compared with smaller majorities of “somewhat conservative” Republicans (63 percent) and those who are moderate or liberal (56 percent).

House Speaker Paul Ryan (R-Wis.) told Republican lawmakers on Oct. 10 that he would no longer support presidential nominee Donald Trump—the start of a messy breakup that will go on through Election Day. (Peter Stevenson/The Washington Post)

Ryan's stand against Trump is being handled differently by several other prominent Republicans. For one, Rep. Rep. Jason Chaffetz (R-Utah) has said that even though he could not endorse Trump or his actions, he still plans to vote for the Republican nominee.

Maryland Gov. Larry Hogan, a popular Republican in an overwhelmingly Democratic state, has spoken out against Trump, a move that was widely popular with independents and Democrats in the state, but Republicans were split on whether they approved of the decision.

This Washington Post-ABC News poll was conducted by telephone Oct. 25 to 28 among a random national sample of 1,781 adults, including landline and cellphone respondents. Overall results have a margin-of-sampling error of plus-or-minus-2.5 points; the error margin is plus-or-minus-three points among the sample of 1,160 likely voters. Sampling, data collection and tabulation are by Abt-SRBI of New York.