Hours before the spot was set to run, however, WMUR-TV had to revise its contract with Senate Majority PAC and credit the group's account. Many of these groups want to keep spending in a final push before next Tuesday's elections, as Democrats defend their Senate majority and Republicans drive for the six seats required to command it. "Campaigns and third-party groups are finding it difficult to even find spots to purchase," said Isaac Baker, who was a top official on the advertising team for President Barack Obama's re-election bid and now advises some of the Democrats' heaviest spenders. New Hampshire's Senate race — which includes media markets in Maine and Massachusetts — is seeing, on average, a threefold increase in overall spending on political advertising. "The sell-out rates are high and ...