Last Tuesday’s contests moved the Republican Party closer to deciding on its nominee, with Donald Trump winning four of five states, including the winner-take-all state of Florida and its 99 delegates. It also shows some interesting trends when mapped out against previous contests:
Trump, Cruz, and Rubio after March 15
One of the most noticeable elements of these maps is that Trumps support stays relatively steady between state contests on different dates, with the exception of Illinois and Missouri, where he shows a higher level of support than in previous contests as evidenced by the noticeability of those two states’ boundaries with previous contests.

Another is that the trend of Rubio’s support dissolving after his poor showing on March 1 continued on March 15 in all but his home state of Florida, with Ted Cruz being the main beneficiary in North Carolina, as he was in Maine and Mississippi.

As can be seen, Ohio is an anomaly where support for Trump’s two main challengers seems to evaporate in favor of support for the fourth candidate in the race, John Kasich.  To give an idea of how much Kasich’s support is contained within the borders of Ohio, here is a map of the states that comprised the Northwest Territory plus Kentucky, which borders Ohio:
Trump, Cruz, and Kasich in the Northwest Territory and Kentucky

As can be seen, Kasich does get more support than Rubio in Illinois and Michigan, but there is a stark difference between his support within and beyond the Ohio borders, reflecting both his personal popularity among Ohio Republicans as well as the massive amount of strategic voting that took place on March 15. Marco Rubio told his voters to vote for Kasich instead in Ohio, and it appears that many voters who would have otherwise supported Ted Cruz did the same in a successful bid to deny Donald Trump Ohio’s 66 delegates.

However, this also bodes ill for Kasich’s chances to repeat his Ohio success in nearby states like Indiana and Pennsylvania and suggests that Trump will do very well in the remaining states east of the Mississippi River.