Washington, Sep 21 (IANS): A slew of new opinion polls shows President Barack Obama gaining advantage over Mitt Romney as his Republican challenger scrambles to put his campaign back on track over his controversial remarks writing off nearly half of Americans as his voters.

An NBC News Wall Street Journal poll in three key battleground states released Thursday showed Obama with slight leads over Romney in Colorado and Wisconsin, and a significant lead in sparsely polled Iowa, where early voting begins next week.

A separate CNN/ORC International poll, also released Thursday, showed Obama slightly ahead in Nevada, 49 percent to 46 percent. That is within the poll's margin of error.

The poll compares to a smaller, 1-point 48 percent to 47 percent Obama lead in a CBS News/New York Times/Quinnipiac University poll released Wednesday.

The NBC/Wall Street Journal survey indicated Obama pulling ahead among likely voters by five points in both Wisconsin and Colorado with 50 percent to Romney's 45 percent, a margin that is within the poll's sampling error. But in Iowa the president holds an eight point lead with 50 percent to Romney's 42 percent, which is outside the poll's sampling error.

The poll shows Romney's favorability also taking a hit with voters in Colorado showing 43 percent favorable to 50 percent unfavorable; in Iowa, it's 42 percent to 50 percent; and in Wisconsin, it's 43 percent to 46 percent.

According to the poll, the candidates remain in a dead heat on voters' perception of whether they will help the economy.

Other recent polls conducted in these swing states also show Obama with an advantage among likely voters. A poll conducted by Marquette University Law School released Wednesday showed the president leading with 54 percent to Romney's 40 percent among Wisconsin likely voters.

The polls came as Romney sought to get over his controversial remarks that 47 percent of Americans were moochers or dependent on government with a new line of attack against Obama seizing on comments the president made about change in Washington Thursday.

"The most important lesson I've learned is that you can't change Washington from the inside. You can only change it from the outside," Obama said at a presidential forum set to run on the Spanish-language network Univision.

Quickly pouncing on the remark Romney said at a Sarasota, Florida, rally: "The president today threw in the white flag of surrender again. He said he can't change Washington from the inside, he can only change it from outside. Well, we're going to give him that chance in November. He's going outside."