WASHINGTON — Top government contractors are ramping up their political giving before the congressional elections, seeking protection from sales-sapping budget cuts.

The 10 biggest contractors, including Lockheed Martin Corp. and Northrop Grumman Corp., boosted political action committee contributions by 29 percent in advance of the 2014 midterm congressional elections compared with 2012, according to Federal Election Commission filings compiled by Bloomberg.

Lawmakers elected on Nov. 4 will help decide the fate of automatic federal spending reductions, which were set at $1.2 trillion over a decade, after a two-year deal easing the cuts expires next year. The companies need Congress’s support because sales are being hurt as agencies tighten spending. Their strategy of pumping up profits through stock buybacks and cost cutting might be difficult to maintain.

“They’ll spend whatever it takes to stifle this trend,” said Mark Amtower, a partner at Amtower & Co., a Clarksville, Md.-based consulting firm specializing in contracting. “Rather than buy back the stock, they want to buy back congresspeople.”

The government’s top 10 suppliers made $13.7 million in PAC contributions during the first 15 months of the current two-year election cycle, which began Jan. 1, 2013. That compares with $10.6 million from Jan. 1, 2011, though March 31, 2012. The leading contractors have given so much money that they now account for three of the five most-generous corporate PACs in 2014.