It also depends on the way the two party system is organized. One point that keeps the American system as polarized as it is is closed primary elections, which guarantee that only the most fervent and 'ideologically pure' candidates are selected. Since only registered party voters can cast ballets, the type of candidates that resonate are elected and continue on to the national election.

In the last elections for example I heard multiple times from friends and family (that identify more with the democrats) that they would have considered voting for someone like Kasich (2016) or Jon Huntsman Jr (2012), but are robbed of that choice because they are blocked from voting in the republican primary.