Three national polls – Fox News/Opinion Dynamics, the Gallup daily tracking poll, and Diageo/Hotline – show Hillary Clinton and Barack Obama in a tie.

The Fox poll, conducted Feb.19-20, has Clinton and Obama at 44 percent each, 8 percent “don’t know,” within a 5 point margin of error. Gallup has Clinton leading Obama 45 percent to 44 percent with a 3 point margin of error. Diageo/Hotline, conducted Feb.14-17, shows Clinton leading Obama 45 percent to 43 percent, well within the 5.1 percent margin of error.

Gallup has bounced up and down over its last nine daily tracking reports, with Clinton and Obama roughly tied early last week, followed by several days of Obama opening up leads of 5 to 7 points, then another virtual tie on Tuesday, and another 5 point Obama lead yesterday that apparently has collapsed again. It will be interesting if any of the pollsters can determine whether a factor in this is the combined attacks by Clinton and John McCain’s on Obama’s experience.

The tie at 44 percent reported by Fox today contrasts to Clinton’s 47 percent to 37 percent lead in its Jan.30-31 poll. Asked if Clinton should pick Obama as her running mate if she wins the nomination, 63 percent of Democrats answered “yes,” but when the question was asked the other way around – should Obama pick Clinton – a lesser 54 percent approved of the idea. Forty-seven percent of Democrats say Obama was most likely to bring about real change to 37 percent for Clinton.

On the Republican side, McCain leads Huckabee 51 percent to 34 percent in the Fox poll, with a 6 point margin of error, but by a much larger 62 percent to 22 percent in the Gallup survey, with a 3 point margin of error. The Diageo/Hotline poll found McCain ahead of Huckabee by 53 percent to 25 percent. All the polls were conducted before the New York Times ran its story last night exploring McCain’s relationship with a female lobbyist in 2000.

About half of Republicans surveyed by Fox said McCain’s positions on the issues were “about right,” while a third said they were not conservative enough. About half also said Huckabee’s positions were about right, but only 13 percent said he was not conservative enough. Fifty-one percent of Republicans said that if McCain wins he should pick Huckabee as his running mate, and 37 percent said he shouldn’t.