Will Newt Gingrich's gas price promise pay off? Tuesday's Trail Mix Former House speaker Newt Gingrich has a lot on the line in today's Alabama and Mississippi primaries - in terms of both the future of his campaign and his focus on the issue of gas prices. Gingrich has campaigned a total of 10 days in both states, compared with six days for former Pennsylvania senator Rick Santorum and four days for Massachusetts governor Mitt Romney. One of the big questions looming over the race right now - particularly if Gingrich wins in these states - is whether he would be able to actually deliver on his promise of $2.50-a-gallon gasoline if he were to become president. The Washington Post's Steven Mufson reports that many oil industry experts and economists say a president has little control over gasoline prices, at least in the short term. What are your thoughts: Is it a typical election-year pledge, or would Gingrich actually be able to pull it off if he wins the White House? Let us know on Twitter with the hashtag #wptrailmix, or send a tweet to @feliciasonmez. And stay tuned to this space later today as we liveblog today's primaries in Mississippi and Alabama as the primaries in Hawaii and American Samoa. 12:50 p.m.: Mitt Romney holds a campaign event in St. Louis, Mo. 1:45 p.m.: Newt Gingrich delivers remarks at the Vestavia Hills Chamber of Commerce in Birmingham, Ala. 3:15 p.m.: Newt Gingrich visits the Birmingham Zoo in Birmingham, Ala. 6 p.m.: Mitt Romney holds a campaign event at William Jewell College in Liberty, Mo. 8:30 p.m.: Rick Santorum holds a primary-night rally at the Hilton Hotel in Lafeyette, La. 9 p.m.: Newt Gingrich holds a primary-night rally at the Wynfrey Hotel in Birmingham, Ala.