Republican rivals Mitt Romney and John McCain are also essentially deadlocked as the White House races in both parties tightened. About half of the polling in the four-day tracking survey was conducted after the Iowa caucuses last Thursday, when Obama and Republican Mike Huckabee sailed to easy wins in the opening test of the US presidential campaign.

Obama, an Illinois senator vying to be the first black president in US history, pulled within one point of Clinton in the state’s Democratic race — a statistically insignificant lead. The poll in both races had a 3.4 percentage point margin of error.

Clinton, a New York senator and former first lady, led Obama 31 percent to 30 percent.

Before Iowa’s caucuses, Clinton led Obama by six points.