AFP

THE Democratic race for the presidential nomination has settled into a pattern. Barack Obama gains momentum, and is nearly crowned the winner. Then Hillary Clinton wins a high-profile contest and makes a comeback, before Mr Obama builds up steam yet again. Mrs Clinton's latest resurrection came with big wins in Texas and Ohio. But now Mr Obama is back. Over the weekend he won a caucus in Wyoming and on Tuesday March 11th he emerged as victor at a primary in Mississippi. He won both by margins of over 20 points.

Mr Obama's recent wins will no doubt gratify him and his campaign team. The victories vindicate further his campaign's strategy: leave no state uncontested, and rack-up support wherever it is to be found. It has allowed him to build a commanding lead of around 150 pledged delegates.

The Clinton team began spinning the two losses before they happened. Both Wyoming and Mississippi are deeply Republican states, which Mr Obama has no chance of winning in the election. According to Mrs Clinton, the states that matter are the big swing states that Democrats need to win in the autumn. These are Ohio; Florida, which she “won” in a primary in which nobody campaigned, since the state broke party rules by holding its vote too early; and Pennsylvania, which goes to the polls on April 22nd and where she likes her chances.

Her argument falls at several hurdles. The delegates she won in Florida will almost certainly not be counted. And although Ohio was a big victory, even a huge win in Pennsylvania would not make up her deficit in pledged delegates.

Both Mrs Clinton and Mr Obama will battle for support from “superdelegates”. These party bigwigs may vote for whom they choose at the convention. Hence Mrs Clinton's parallel campaign to convince them that the rules of the game are tilted away from her unfairly. She says that caucuses, which Mr Obama has dominated, are undemocratic. Her team also complains of unfair press coverage.

Winning over the superdelegates with such arguments could be rough and divisive enough. Worse still, Democrats may get such arguments for all 42 days between the primaries in Mississippi and Pennsylvania. Bored and frustrated, the two candidates and their many surrogates could settle into mutually destructive trench warfare.

The nastiness has already begun. Samantha Power, an unofficial Obama adviser, had to quit after calling Mrs Clinton a “monster” in a newspaper interview. But more of the ugly stuff has come from the other side. Mrs Clinton has suggested, in an ad and in her comments, that she is ready to be commander-in-chief, as is the Republican nominee-to-be, John McCain, but that Mr Obama is not. Her spokesman compared Mr Obama to Ken Starr, whose investigations of the Clintons in the 1990s made him a hate-figure among Democrats. And last week, a newspaper printed comments by Geraldine Ferraro, a prominent supporter of Mrs Clinton, that are angering blacks, hitherto a solid Democratic-voting block.

Mrs Ferraro, the Democratic vice-presidential candidate in 1984, said that Mr Obama was only where he was in the race because he was black. Race being as ticklish a subject as it is in America, most politicians would retreat and praise Mr Obama when such comments caused a stir. Instead Mrs Ferraro said that the outcry made her a victim of reverse racism. A spokesman for Mrs Clinton has said only that she “disagrees” with Mrs Ferraro's comments. The Obama team asks why, if Ms Power had to quit, Mrs Clinton does not disown Mrs Ferraro. And if she doesn't, Mr Obama's supporters may lash out in frustration.

A campaign that degenerates into name-calling and mud-slinging will hurt Mr Obama more than it does Mrs Clinton. He has campaigned on messages of “change” and “hope” so he faces an unenviable choice in the long run-up to Pennsylvania. If he lets the Clinton team fling the brickbats without retaliation she may set the tone of the campaign. But respond in kind and his message of a new politics is tarnished. Even though he is behind there in the polls, Pennsylvania cannot come soon enough for Mr Obama.