The monster storm battering the East Coast is hurting both presidential candidates. But it is probably hurting Mitt Romney more.

By freezing the campaign in its tracks, Hurricane Sandy is blunting the momentum that Romney had achieved since the debates, which put him ahead of President Obama in many national tracking polls and had him edging ahead or closing the gap in several key swing states. With the killer storm now dominating the news, Romney faces the challenge of keeping the conversation on politics when tens of millions of Americans are focused on anything but.

Romney’s progress, at least as measured by polls, may have been petering out anyway before Sandy struck. But from the viewpoint of a challenger trying to make the sale, the storm is an unwelcome October surprise.

To underscore Romney’s dilemma from an appearance standpoint, the president is assuming control of the federal emergency response. Obama flew to Florida on Sunday night, but canceled an Orlando event scheduled for Monday morning to return to the White House to monitor the storm’s damage. Romney, by contrast, has no role other than to express sympathy.

The hurricane takes two critical states, Virginia and New Hampshire, off the campaign trail this week. The candidates simply can’t bring their Secret Service details and motorcades into storm-ravaged areas trying to cope with flooding and blackouts. This could undermine Romney’s effort to close the gap in Virginia, where the latest Washington Post poll gives Obama a 4-point lead. The president has a 2-point lead in New Hampshire, according to a PPP poll.

Both candidates are likely to double down in Ohio, which is mostly outside Sandy’s path. Obama had been clinging to a 4-point lead in that bellwether state, but a Cincinnati Enquirer survey now has them tied at 49 percent. Romney has fewer paths to 270 electoral votes without Ohio.

The storm and its aftermath could hurt Obama’s ground operation, which is widely acknowledged to be stronger than Romney’s and is a linchpin of his strategy. By sidelining staffers, and making potential voters harder to reach by phone, the hurricane could put a serious crimp in the Obama turnout machine. Obama is also banking more heavily on early voting—Maryland shut down its program for Monday—but many of the affected states have tight restrictions on such voting.

Still, the greatest impact may be on public attention. Go to any news website or flip on any cable news channel, and Sandy is the dominant story by far. No one is talking about tax cuts or unemployment or immigration. Television has a tendency to overhype major storms, but given the breadth and destructive power of Sandy, the saturation coverage seems to match its magnitude.

Obama can now cast himself as a take-charge executive, meeting with FEMA officials and directing the government’s response. This approach is not without risk, as George W. Bush learned after Katrina. But it casts Obama in a more presidential role than simply touring the country giving the same stump speech.

Romney is doing the only thing he can do, which is trying not to appear preoccupied with politics. “I know that right now some people in the country are a little nervous about a storm about to hit the coast,” he said. “And our thoughts and prayers are with the people who will find themselves in harm’s way.”

By Nov. 6, Sandy may prove to be a political afterthought. But in such a tight race, it now looms as a powerful X factor.