Rubio's path includes the following:
-An inauguration event.
-Choosing a SCOTUS Justice to replace Scalia, which will set the trend for Rubio's future picks (all of the remaining incumbent Justices are old enough that they could conceivably retire or die in his term). His choices include:
Lorie Skjerven Gildea, the current chief of the Minnesota Supreme Court and a center-right judge; either Ted Cruz, if Cruz wasn't chosen as VP, or Cruz's mentor J. Michael 'Mike' Luttig if he is the VP, both being the hardline right-wing choices; and
Sri Srinivasan, a centrist judge that was one of Obama's possible picks for an early Scalia replacement.
-Culture War events dealing with the Supreme Court repealing Roe v. Wade (the abortion decision, struck down with a center or far-right Justice) and Obergefell v. Hodges (the gay marriage decision, only downed by a far-right Justice), or neither (if the centrist Justice is chosen).
-Economic downturn in the middle of 2017. Rubio can either attempt Obama/Bush-style stimuli & bailouts or do nothing in the name of the free market.
-Ramming an 'amnesty' (a path to legalization and citizenship for illegal immigrants) bill through Congress in 2017. Passing it upsets both traditional conservatives and the alt-right, not passing it upsets liberals and the Establishment (fewer immigrant workers to exploit). An option to prevent this will exist if Rubio chose Cruz as his VP.
-Renewing the US Freedom Act in 2019. This is an event for all Presidents: can choose to renew it as-is (the NSA remains powerful but no longer has the authority to collect phone data without a court order), renew it and restore the NSA's phone-data collection authority, or let it expire. However, depending on the President in charge or their chosen VP, some of these options may not be available. In Rubio's case, he can only choose the option to let the Freedom Act expire if he has Cruz as VP, as Cruz is trying to reach out to the Paulite libertarians and/or has a much more sinister purpose in mind (see below).
-Assassination attempts on Rubio by Cruz: if he made Cruz VP but then pissed off the social and economic conservatives by choosing a centrist Justice who won't turn the Culture War around AND trying to intervene in the economy when it crashes in 2017, in late 2019 Cruz will attempt to assassinate him together with some especially radical far-right militia movements. If Rubio renews/strengthens the Freedom Act, the NSA will expose the plot and the FBI kills or arrests the militiamen, forcing Cruz to flee Washington and setting the stage for a civil war where Rubio has the upper hand. On the other hand, if Rubio took a VP Cruz's advice and lets the Freedom Act expire, the NSA will be unable to prevent the plot and Cruz manages to kill Rubio without leaving any particularly damning evidence, which will probably also start a civil war but one where Rubio is obviously too dead to restrain Cruz.
-Rubio assassinated by the Establishment: if Rubio refuses to do their dirty work by opposing both amnesty and the Freedom Act, the Establishment will turn on their 'golden boy' and have him poisoned at a state dinner. This will only happen if his VP is either Nikki Haley or Scott Walker, since even if the Establishment comes to hate the very ground he walks upon they still won't want to make Cruz President.
-A civil war started by the left wing: If Rubio goes too far to the right by appointing both a hard-line Justice to SCOTUS (either Cruz/Luttig) and by refusing to do anything to help the US economy when it flounders in 2017, in late 2019 left-wing agitation reaches the critical mass for a civil war.
-A civil war started by the far-right: If Rubio drifts too far to the left but doesn't make Cruz his VP, instead of the assassination attempt Cruz (who is locked out of the presidential line of succession in this case) will openly incite a right-wing rebellion against him in late 2019.
-The economy starts recovering in 2018/19, if Rubio chose to go down the Bush/Obama path of semi-Keynesian bailouts and stimuli.
The civil war faction event-flags I've used are:
CON_FURY: Representing traditional conservative agitation. Increased by nominating a centrist Justice, intervening in the economy & granting amnesty to illegal immigrants.
LIB_FURY: Representing social liberal & progressive agitation. Increased by nominating right-wing Justices who strike down Roe v. Wade and/or Obergefell v. Hodges, not intervening in the economy and not granting amnesty to illegal immigrants.
LIBR_FURY: Representing libertarian agitation. Increased by renewing or strengthening the Freedom Act in 2019.
ESTB_FURY: Representing Establishment agitation. Increased by not granting amnesty to illegal immigrants and letting the Freedom Act expire in 2019.
ALTR_FURY: Representing alt-right (irreligious far-rightists, ex. Neo-Nazis) agitation. Increased by granting amnesty to illegal immigrants.
I currently have no events for a civil war started by libertarians, the Establishment or the alt-right under Rubio. I think the libertarians & alt-right are too small to try anything on their own (they would rather wait for the larger traditional conservative or liberal factions to start it, then rise up in the ensuing chaos - rising up alone would likely get them destroyed fast) and the Establishment is a fan of Rubio's anyway. Anyway, my idea was that the higher the number of the flags set, the stronger that faction's rebel forces would be (ex. the left-wing rebellion with the LIB_FURY_1, LIB_FURY_2 and LIB_FURY_3 flags set would be stronger than just with LIB_FURY_1 and 2 set).
Rubio can also prevent a civil war (at least one involving broad left/right strokes) without getting assassinated if he carefully balances both wings' preferred policies. He must nominate the CENTER-right Justice who will strike down Roe v. Wade but not Obergefell v. Hodges, which makes the right happy and the left upset but not completely livid; then he must intervene in the failing economy, which appeases the left and angers the right, but not to the point where they're prepared to engage in civil war and/or assassinate him. Lastly he must appease the Establishment at least once, by either passing an amnesty bill or renewing/strengthening the Freedom Act.