Clear the way for Trump candidacy - Haley drops out. If Trump wins the election, his policies are likely to become much more extreme.
Further US support for Ukraine, which is being attacked by Russia, is then at stake in foreign policy terms. US membership in important international alliances such as NATO is also at stake. The actual presidential election is on November 5th. Anyone who wants to become the Republican or Democratic presidential candidate in the USA must first win the party's internal primaries. The presidential candidates will not be officially chosen until party conferences in the summer.