There are at least 300 delegates up for grabs in the March 4 Democratic contests in Ohio, Texas, Rhode Island, and Vermont.

Sens. Barack Obama, D-Ill., and Hillary Clinton, D-N.Y., launched a barrage of television spots in Ohio and Texas. Some analysts and insiders say it's do-or-die time for Clinton's campaign that suffered 11 straight losses since Super Tuesday, The New York Times noted.

Obama's drive erased her near double-digit lead in both states, but Clinton is vowing to soldier on with her candidacy beyond Tuesday, believing she can win enough delegates to stay competitive.

Clinton's chief strategist, Mark Penn, said Obama's television bitz is a sign that the mania surrounding his campaign is in decline.

Obama's campaign flew 200 organizers to Texas after the Feb. 5 Super Tuesday contests and Clinton supporters launched get-out-the-vote drives in both states at their own expense.

Both candidates catered to the blue-collar demographic in Ohio and Latin and African-Americans in Texas.