By Grant Smith

NEW YORK (Reuters) - Democratic presidential nominee Hillary Clinton has a 6-percentage-point lead over Republican rival Donald Trump, according to a Reuters/Ipsos tracking poll released on Tuesday.

Clinton's support has ranged from 41 percent to 44 percent since late July, and was about 41 percent in the Aug. 11-15 online poll.

Trump's support has experienced wider shifts ranging from 33 percent to 39 percent while his campaign has endured controversies and distractions in recent weeks. He is favored by about 35 percent of likely voters, according to the most recent poll.

Trump has caused divisions in the Republican Party with his strong anti-immigrant and anti-Muslim rhetoric, and faced criticism from both parties earlier this month for a days-long feud with the parents of a Muslim American Army captain killed in Iraq. Last week, 70 Republicans, including former members of Congress and Republican National Committee staff, wrote a letter calling for the RNC to stop helping Trump, whose actions they said were "divisive and dangerous."

The number of likely voters who picked neither Clinton nor Trump in the poll was nearly 24 percent.

At this point in 2012, President Barack Obama was ahead of Republican nominee Mitt Romney by nearly the same margin, favored by 46 percent of likely voters to Romney's 41 percent, with about 13 percent picking neither candidate.

Obama and Romney swapped the lead in the poll several times through the summer and early fall before the president took and held the lead in late October.

In a separate Reuters/Ipsos poll that gave respondents the option to choose from Clinton, Trump, Libertarian candidate Gary Johnson and Green Party candidate Jill Stein, Clinton also led Trump by 6 percentage points.

Of the alternative party candidates, Johnson came in third with 8 percentage points. Stein had about 2 percentage points.

The Aug. 11-15 polls surveyed a sample of 1,132 and 1,131 likely voters, respectively, and had a credibility interval of 3 percentage points.

(Editing by Jonathan Oatis)