WASHINGTON (Reuters) - Mitt Romney's selection of Paul Ryan as his running mate has done little to attract voters to the Republican ticket and more think he is not qualified to be president than believe he is ready for the White House, a Reuters/Ipsos poll said on Monday.

Fewer than a third of registered voters, 29 percent, said the selection of Ryan made them feel more favorable toward Romney. But with 27 percent in the online poll saying it made them feel less favorable, Ryan's place on the ticket may have little effect on the November 6 election.

The results were largely split along party lines - with 46 percent of Democrats saying Ryan's choice made them less favorable, compared with 8 percent who said the opposite. And 56 percent of Republicans felt more favorable, versus 6 percent.

But Ryan has not swayed many political independents, the voters expected to play a decisive role in the election. Eighteen percent felt more favorable and 13 percent less so.

"Overall, he doesn't really appear to be impacting the top of the ticket much," Ipsos pollster Julia Clark said. "He's still a bit of an unknown entity."

The survey was conducted September 20-24, a time when some Republican commentators have been pressing Romney's campaign to do more to promote Ryan, who is seen as a proponent of big fiscal ideas, like a plan to overhaul the government Medicare health insurance program for retirees.

The Washington Post reported on Monday that some conservatives think Romney's campaign has been too cautious by avoiding Ryan's big ideas and hoping that President Barack Obama will defeat himself.

Polls have given Obama a steady nationwide lead over Romney since the Democratic convention early this month. The Reuters/Ipsos tracking poll on Monday had Obama leading by 49 percent to 43 percent for Romney among likely voters.

"Obama's now been healthfully in the lead since the convention. If he can sustain this for another 45 days, it's done," Clark said.

BIDEN BENEFITS FROM INCUMBENCY

Forty-four percent of registered voters think Ryan is not qualified to be president, compared with 29 percent who feel he would be ready to step into Romney's shoes if necessary, the survey found.

A larger percentage thought that Joe Biden, 69, the incumbent Democratic vice president, is ready for the Oval Office. Biden led 43 percent to 36 percent, thanks to huge support among Democrats.

But more Democrats had faith in Biden, a former Delaware senator who is well-known as the incumbent, than Republicans had in the 42-year-old Ryan, a Wisconsin congressman who is chairman of the House of Representatives Budget Committee.

Among Democrats, 74 percent said Biden was more qualified, versus 8 percent who chose Ryan and 18 percent who did not know. Seventy percent of Republicans favored Ryan, compared with 13 percent for Biden and 18 percent who did not know.

The numbers were even among independents, with 30 percent each for Biden and Ryan, and 40 percent who did not know.

More registered voters have heard of Ryan than before Romney selected him, but he still falls short in national name recognition. Only 56 percent of registered voters said they were familiar with Ryan, versus mid-August's 35 percent.

Their opinions of him are split evenly. Forty-nine percent view Ryan favorably, versus 51 percent who don't, divided largely along party lines. Among independents, 48 percent view him favorably and 52 percent don't, the poll showed.

The precision of the Reuters/Ipsos online polls is measured using a credibility interval. In this case, the poll has a credibility interval of 3.1 percentage points for the 1,313 registered voters surveyed and 3.5 percentage points for the 1,095 likely voters.