Wilson Tucker - The Year of the Quiet Sun

Plot summary according to Wikipedia:

During a vacation on a Florida beach in the summer of 1978, Brian Chaney, a demographer and biblical scholar, is approached by a woman named Kathryn van Hise. Initially assuming her to be a reporter interested in a controversial book he just published on the Dead Sea scrolls, she informs him that she works for the federal Bureau of Standards and that she is recruiting him for a physical survey of the future via a secretly constructed "TDV" or time displacement vehicle. When Chaney demurs, she informs him that his contract with has been purchased from the think tank where he works, leaving him little choice.

The reluctant Chaney travels by armored train to a military installation south of Joliet, Illinois. There he is teamed with two diversely talented military officers, United States Air Force Major William Moresby and United States Navy Lieutenant Commander Arthur Saltus. Chaney soon finds that he shares with Saltus an attraction to Kathryn, who is their civilian liaison, but unlike Saltus, Chaney lacks the assertiveness to pursue her aggressively. Instead he focuses his attention on the project, which is soon ordered by the President of the United States to embark on their first mission, a trip two years into the future to discover whether he wins the 1980 presidential election.

The three travel to the Thursday after the election on individual trips, with first Moresby and then Saltus going first according to military seniority. Chaney, as a civilian, is the last to leave, but arrives earlier than the others due to a temporal navigation instrument error. They discover that the president, whom Chaney despises as a weak man (in fact, his name is given as "President Meeks"), wins the election in a landslide as a result of his successful handling of ongoing race riots in Chicago, and that these riots have resulted in the building of a wall down the middle of Cermak Road dividing the north of the city from the south. They also learn that the nation is under martial law after a failed attempt by the Joint Chiefs of Staff to take over the government by coup d'état, one thwarted because of the advance knowledge the time travelers will bring back of it. While preparing for their return...

In her analysis of the book, Sandra Miesel praised the novel as "an intimate drama of Armageddon played out within the boundaries of Will County, Illinois by a cast of five principals." She noted the way Wilson linked the America of the novel and the Qumran community of ancient Palestine, which are introduced through Chaney's background as a biblical scholar who had published a book on the Dead Sea scrolls prior to the start of the novel. The parallels were made explicit through Biblical motifs that appear throughout the novel, with characters paralleling types out of the Dead Sea scrolls and such apocalyptic imagery as a radioactive Lake Michigan substituting for the lake of fire in the Book of Revelation.

Take a look at Michael K. Smith review of the book in Amazon.com and what he has to say about the author:

"Arthur Wilson Tucker, known throughout science fiction fandom as "Bob," was not a scientist like Asimov or Benford. He was, in fact, a motion picture projectionist from Illinois who wrote mysteries and science fiction stories and novels on the side, beginning in 1941. This book and 'The Lincoln Hunters' are certainly his best (and best known) work, but there was another whole side to him -- the raconteur and noted wit who hung out with the "ordinary" fans at WorldCons, and who held forth at hotel room parties on the benefits of bourbon ("Smoooooth!"), and who cheerfully distributed business cards with only his name on one side and the words "Natural Inseminations" on the reverse".

 
Nobody seems to have enjoyed the book a great  great deal at Amazon reviews but I did. A bit "old", perhaps not too well aged, but charming and funny nevertheless on my opinion. Time travel was a favourite topic of the 70's and it's kind of used nowadays but...