Since taking office in 2009, President Barack Obama has only had to use his veto power twice. The reasons for this are quite simple.
In his first two years in office, he had a fully Democrat-controlled Congress. So, only "friendly" Senate and House bills were sent to the President for his signature. Thus, they never put the President in the politically awkward position of having to veto a bill. Then, since 2010, when the House of Representatives went to Republican control, Harry Reid managed to shield the Obama from using his veto power by simply sitting on more than 350 bills that the Republican House had sent over to the Democrat Senate. Some are being tied up in Democrat-led committees; while the rest are just withering away because Harry Reid won't bring them to the floor for a vote.
If the Senate turns Republican, Reid will lose his majority leadership and all the Senate committees will become controlled by Republicans. As a result, many of those idled bills will start being passed and sent to the President for his signature. Now, most of those bills are not going to be to Obama's political and ideological liking. Especially the ones that would kill or delay ObamaCare. So, expect a flurry of vetoes that have never been seen in this country before. Then Obama will be seen as the obstructionist. Not Congress.
But, another interesting thing might happen with the vetoing of so many bills. The President's approval rating may drop significantly. That drop may force some Democrat Senators who are up for, and at risk of losing reelection in 2016, to distance themselves from him by joining the Republicans in overriding those vetoes. Of course, that will force Obama to use even more executive orders in order to counter any those bills where his veto was overridden.
Lastly, when Senate Majority Leader Harry Reid successfully implemented the so-called nuclear option in the Senate, he literally blew up the minority party's ability to use a filibuster to block the passage of certain bills and, the requirement of a minimum of 60 yea votes to approve the President's nominees to the judicial bench or to any positions in his Administration. As a consequence, the Senate Republicans lost the ability to do anything to block bills or block presidential nominees. Many seem to think that, if the Senate goes Republican, the majority leader will reverse the nuclear option. I don't think so. By once again, requiring a 60-vote override of the filibuster, many of those 350 bills in the Senate won't reach cloture and won't even be sent to the Senate floor for a vote because they will just remain tied up in a filibuster by the Democrats. Thus, if the Senate does go to the Republicans, the minority party Democrats will deservedly find themselves hoisted up on their own petard because they foolishly and selfishly implemented the nuclear option.
Ah yes. the President's last two years in office could be quite interesting as both he and Congress battle it out in what could only be envisioned as an all out war.
Veto Counts by President: http://www.senate.gov/reference/Legislation/Vetoes/vetoCounts.htm
Stack of 350 Bills Stuck in the Senate: http://www.texasgopvote.com/issues/grow-economy/stack-350-bills-stuck-senate-006985