What key factor contributed to the accounting firm's ability to make a claim in federal court?

The key factor that enabled the accounting firm to make a claim in federal court is that the negligence claims were transactionally related. This indicates that the claims arose from a common nucleus of operative fact, which is crucial for establishing jurisdiction in federal court, particularly under supplemental jurisdiction rules. When multiple claims share a significant factual basis, the court can assert jurisdiction over those claims even if they may not independently qualify for federal jurisdiction.

While the other factors might imply a connection to federal court jurisdiction, they do not directly address the underlying relationship of the claims themselves. For instance, involvement with an international client may lead to federal interest, but it does not inherently establish jurisdiction without a common factual link. Similarly, claims involving amounts exceeding $75,000 or matters of federal law interpretation can offer standalone bases for federal jurisdiction but are not dependent on the interconnectedness of multiple claims. The transactional relationship among the claims is what solidifies the basis for proceeding in federal court.