Poll: Donald Trump chips away at Hillary Clinton's national lead

Must Read: How healthy are Clinton and Trump?
Must Read: How healthy are Clinton and Trump?

Hillary Clinton's national lead over Donald Trump has narrowed slightly to 6 points, according to the latest NBC NewsSurveyMonkey Weekly Election Tracking Poll.

Clinton now enjoys 48 percent support, while Trump holds steady with 42 percent. Last week, Clinton led Trump by 8 points. The latest NBC NewsSurveyMonkey poll was conducted online from August 22 through August 28 among registered voters.

In a four-way general election match-up, Clinton leads with 41 percent, a 4-point margin over Trump (37 percent). Libertarian Gary Johnson maintains 11 percent of the vote and Green Party candidate Jill Stein holds steady with 5 percent.

Given the highly partisan nature of voting, it's clear there are not that many voters who are persuadable. Since both parties' conventions last month, a roughly equal number of Republicans and Republican-leaners support Trump and an equal number of self-identified Democrats and Democratic-leaners support Clinton.

The one group that is open to changing their minds are registered Independents who do not lean toward either party. Trump has made inroads with this group. Two weeks ago, Clinton led Trump by 12 points among this key group of persuadable voters — 40 percent to 32 percent. This week, that lead is down to just 4 points — 37 percent to 33 percent.

The presidential campaign will enter a final phase after Labor Day, when there will be an increase in political advertising in battleground states and final appeals will be made to those few voters who have yet to make up their minds.

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RCP General Election Poll Average - Clinton vs. Trump InsideGov

Though the tracking poll shows that Trump may be closing the gap against Clinton among Independent voters, another key question for both campaigns is whether these non-partisans will be motivated to vote at all. According to data from this week's tracking poll, 70 percent of Independents who now support Clinton say they have supported someone else in the past six months. Among those Independents who currently support Trump, 64 percent say they supported someone else in the past six months.

RELATED: Important people who support Hillary Clinton

The NBC NewsSurveyMonkey Weekly Election Tracking poll was conducted online August 22 through August 28, 2016 among a national sample of 24,104 adults who say they are registered to vote. Respondents for this non-probability survey were selected from the nearly three million people who take surveys on the SurveyMonkey platform each day. Results have an error estimate of plus or minus 1.0 percentage points. For full results and methodology, click here.