The Post-Convention Bounce: What to Watch for in Trump vs. Clinton

For decades, political conventions have marked one of the best moments to plead your case to the American electorate and generate momentum headed toward November.

In the past, most political conventions were held several weeks apart, giving each party an opportunity to push their message and candidates -- and giving pollsters enough time to adequately measure the so-called "convention bounce."

The convention bounce is a small -- or sometimes not-so-mall -- bump in a candidate's support after the forceful messaging and increased media attention during that party's convention.

Here's what to watch for in the coming days.

What We've Seen So Far

We haven't seen any new polls released since the Democratic convention just Thursday, and most quality polls won't be released for a few days. But two polls were released shortly after the Republican convention last week.

These polls showed mixed results. Donald Trump saw a 10-point bump in a CNN/ORC poll, climbing from 42 percent support to 48 percent, his highest support since last September.

On the other hand, a CBS poll out the same day showed no net bounce for Trump at all.

Still, these polls showed other good news for the Republican nominee. Hillary Clinton hit a new low in her honest and trustworthy score in the CNN poll, with almost seven in 10 Americans saying they believe she is not honest and trustworthy.

What Have We Seen in the Past?

For the last two election cycles, the conventions have given slight tweaks to the race that have propelled the candidates toward Election Day.

In 2012, Barack Obama and Mitt Romney were nearly tied, with 47 percent for Romney and 46 percent for Obama, in ABC News/Washington Post polling. But after the convention stretch ended, Obama had opened up a six-point lead, 50-44 percent.

In 2008, John McCain was able to narrow the gap. Obama lead by six points before the convention, 49 to 43 percent. But a poll after the conventions put McCain within the margin of error, 47-45 percent.

Before that, it was not uncommon for candidates to get double-digit boosts in their support after their convention, which usually stood alone, several weeks apart from the other party's.

What Could Be Coming

It remains to be seen how much of a bump Hillary Clinton will pick up after the Democratic convention, so we'll be watching the next round of polling to determine whether she gained ground over Trump or whether Trump has kept the race at the dead heat.

Still, the convention bounce isn't the only thing that matters. Debates begin between Trump and Clinton in late September, and more interviews and campaign events are sure to shape the race from here.

And political journalists also look for the "October surprise" -- an unexpected event just weeks before the election that can shape the outcome.

ABC News' Gary Langer contributed to this report.