With a win in Mississippi Tuesday, Illinois Sen. Barack Obama added a few more delegates to his lead in the race for the Democratic nomination.

But with no elections until Pennsylvania until April 22, his opponent, New York Sen. Hillary Clinton, has a powerful ally on her side: time.

The upcoming 5-6 week stretch marks by far the longest pause for Clinton and Obama in this year’s unexpectedly long nomination fight.

That gives Clinton a chance to wage war on Barack Obama without the time pressures that magnify every moment on the trail, allowing her to make a deliberate, methodical case in favor of her candidacy and against his.

Obama has drawn considerable momentum in the race by winning caucuses and primaries - such as Saturday in Wyoming and Tuesday in Mississippi.

But as we saw in the run-up to March 4 primaries in Texas and Ohio, Clinton has proved adept at controlling the race when no one is voting.

Clinton has already stepped up the pressure on Obama, saying he’s not ready to be commander in chief, attacking him over NAFTA and comments by his adviser; and by suggesting publicly that Obama could be her running mate.

The lull in the voting is also likely to include several debates in Pennsylvania, a format in which Barack Obama does well, but Hillary Clinton excels.

It will also allow the Clinton campaign to work to find a way for Florida and Michigan delegates to be seated or have those states’ votes count.

Both states favor Clinton demographically, and any solution that allows the delegations to be seated at the convention is likely to cut Obama’s lead.

Pennsylvania is also a large, diverse and traditionally blue-collar state that’s similar to others that have leaned toward Hillary.

Clinton has maintained a solid lead in Pennsylvania polls, and Obama’s advisers acknowledge that he is the underdog in the Keystone State.

Right now, Obama has to be considered the slight favorite of the two Democratic front-runners, by virtue of his delegate edge in addition to his overall advantage in the popular vote, and his superior fundraising capacity.

Barack Obama would be wise to tout those advantages - making a claim that he is winning the Democratic race - over the next month and a half.

Barring an unlikely series of blowouts, Clinton will not be able to catch him in delegates, since the Democrats allocate delegates proportionally.

But neither Obama nor Clinton can officially clinch the nomination without significant support from superdelegates, the 796 party leaders who receive automatic convention votes and can support whomever they choose.

Slightly less than half of the superdelegates have not publicly committed to either candidate, and all are free to change their minds.

Clinton’s victories in the Ohio and Texas March 4 primaries appear to have frozen undecided superdelegates. Only four chose a side (all Obama) since.

The several hundred undecided superdelegates, therefore, are by far the most important audience for both candidates to reach.

Some insiders feel that the superdelegates should feel free to make their decision based on who they believe the stronger candidate will be.

Others, including this site, feel that if the “supers” overturned a victory in pledged delegates, it would be tantamount to the end of democracy as we know it.

But with Pennsylvania next on the docket, for the first time since Super Tuesday on February 5, Clinton will go in with the higher expectations: Anything short of a decisive win will be viewed as a disappointment.

And while she has been more adept at shaping the race of late, Hillary Clinton can be overtly negative - something that could backfire, but could also prove successful if Obama isn’t prepared to respond in kind.