Markey and Lynch, meantime, hope to reschedule their planned debate for next week — possibly Wednesday — meaning it would fall less a week before the April 30 primary. 

The timing will give the showdown added importance and raise the stakes for Lynch, who is widely considered the underdog in the race. 

Both Democratic candidates and all three Republican hopefuls — Winslow, former Navy SEAL Gabriel Gomez and attorney Michael Sullivan — put their campaigns on pause after Monday's bombings. 

Even so, the Senate candidates haven't kept entirely low profiles. 

GOP contender Gabriel Gomez did a round of media interviews on Tuesday recounting his experience running in the marathon. He finished shortly before the bombs went off. 

Gomez is "assessing hour by hour" how to move forward with the campaign, but he will likely resume television advertising on Friday, according to a spokesman.

Sullivan, a former acting director of the Bureau of Alcohol, Tobacco, Firearms and Explosives, was also visible in the wake of the bombings, providing expert opinion in a number of television interviews. He plans to resume campaign activities after Thursday's service.

Markey took his TV ads off the air following the bombings. But he issued a blast email praising the response to the bombings from first-responders and volunteers, and directing supporters to a government site listing resources to help.

The continued activity, though not ostensibly campaign-related, reflects the necessity for candidates to remain in the public eye with just under two weeks left until the primaries.