It's "rigged" in a few unquestionable ways:
(1) Our voting system gives disproportionate voting power in both the Senate and the Electoral College to those who live in low-population states. These are mostly red states. In fact, of those living in states with more than the median state population, blue-staters outnumber red-staters more than two-to-one, creating a heavy conservative tilt from this effect.
(2) Our voting system in the House has been gerrymandered by the Republicans in control of most of the states to the point that it's possible (and has actually occurred recently), for the Democrats to receive a significant majority of votes in the House and yet for the Republicans to win a significant majority of the seats.
(3) The disenfranchisement of prisoners not only disproportionately strips the poor and minorities of voting power, but it also disproportionately gives voting power to people in a handful of mostly rural, conservative districts, in red states, where those prisoners tend to be held. The incarceration rate is over three times as high in some states as others, and those people still count for apportionment, giving the voters in those states the equivalent of extra votes. The high-incareration-rate states are ALL red state.
(4) The disenfranchisement of former felons does even more to shift voting power disproportionately away from the poor and minorities, especially in red states, where 5%-10% of potential voters can be disenfranchised,
compared to less than 1% in blue states.
(5) Polling places are set up to make voting as quick and painless as possible in neighborhoods with rich people and white people, while the process is kept difficult and slow in neighborhoods of minorities and the poor, to try to suppress turnout. This results in
black people having to wait in line about twice as long as whites to vote, on average.
(6) People in DC and the territories lack full voting rights (and in some cases any voting rights). These territories tend to favor Democrats by huge margins.
Yes, as skewed as our system is, by design, against the interests of urbanites, the poor, and racial and ethnic minorities (and against the party that serves them), the Republicans would very much likely to skew it even further, with voter ID laws designed to disproportionately inconvenience demographics that favor the Democrats.
There are also the intentionally over-zealous voter purges, and constant attempts to intimidate voters from demographics believed to favor Democrats (e.g., distributing materials in poor and minority neighborhoods warning that anyone with outstanding tickets might be arrested at voting stations, or distributing materials at colleges warning that it is illegal to vote in their home state (or the state where they're going to school -- the point is to spread confusion to scare away voters).
The result of all of that is pretty clear. Republicans consistently do better with "likely voters" than they do with the general populace... because the portion of the general populace most likely to prefer Democrats has had their voting systematically suppressed, while the portion of the general populace most likely to prefer Republicans is disproportionately likely to be located somewhere that their votes count extra. That's certainly a form of rigging an election.
