President Obama narrowly leads Mitt Romney in three battleground states less than a week before the election, according to new NBC News/Wall Street Journal polls.

Getty Images

In Iowa, the heartland launchpad for every presidential bid, the Democratic incumbent draws 50% to 44% for his Republican challenger.

(Read More: .)

In Wisconsin, homestate of Republican vice presidential candidate Paul Ryan, Mr. Obama draws 49% to 46% for Mr. Romney.

And in New Hampshire, the lone Northeastern state Mr. Romney could win, he trails the president by 49% to 47%.

(Read More: .)

All three telephone surveys of likely voters were conducted for NBC and the Journal on Oct. 28-29 by the Marist College Institute for Public Opinion. The margins of error are 2.9 percentage points in Iowa, 3 percentage points in Wisconsin, and 3.1 percentage points in New Hampshire.

The three states, among the nine swing states most closely contested by both parties, were all carried by Mr. Obama four years ago. To attain the 270 electoral votes needed to win the presidency, Mr. Romney needs to carry most of those nine on Election Day.

(Read More: .)

Mr. Romney has been counting on holding the upper hand on the economy. But in Iowa, Wisconsin and New Hamphire, Mr. Obama stands either even with Mr. Romney on that issue or within the margin for error.

Mr. Obama has been counting on his superior personal ratings. But Mr.Romney's ratings have improved during the campaign; only in Iowa among the three swing states do more voters view him negatively than positively.

And both candidates have been counting on a gender gap in their favor.

(Read More: .)

In all three states, Mr. Obama enjoys a double digit lead among women — larger than Mr. Romney's lead among men.

—By CNBC's John Harwood
@JohnJHarwood