A Look At What's Behind Donald Trump's Climb in New National Poll

— -- The latest national ABC News/Washington Post poll has Donald Trump in the tightest race yet with Hillary Clinton in the probable matchup between the two likely presidential nominees.

Forty-six percent of respondents favor Trump over Clinton versus 44 percent who prefer a Clinton presidency. Even though Trump's lead is still within the margin of error, it is notable.

Trump’s enhanced competitiveness reflects consolidation in his support since his primary opponents dropped out, and it comes despite significant challenges to his candidacy.

Fifty-eight percent of Americans call him unqualified to be president; 60 percent see him unfavorably overall; 76 percent think he doesn’t show enough respect for those he disagrees with; and 64 percent say he should release his tax returns -- with most feeling strongly about it. These include majorities of registered voters on each item, representing opportunities for Clinton.

In the last ABC News/Washington Post poll from March 3, Clinton was leading with 50 percent support versus Trump's 41 percent.

Clinton leads among women, non-white voters, college graduates and voters between the age of 18 and 39 years old. By contrast, Trump leads with men, white voters, voters without a college degree and all voters over 40 years old.

Trump has the lowest favorability rating of all three remaining candidates (37 percent) and the highest unfavorability rating (60 percent).

Clinton comes in second with 44 percent favorability and 53 percent unfavorability. Sen. Bernie Sanders is the only remaining candidate who is more liked than disliked, with 51 percent of respondents reporting a favorable view oh him.

The strong feelings voters have about the candidates are impacting their support. Of the registered voters who say they plan to vote for Trump in November, a majority says they mainly oppose Clinton than actually support the New York businessman.

By comparison, the registered voters who plan to vote for Clinton are split over whether or not their vote is a result of their support for the former secretary of state or their opposition to Trump.